1. Field of the Invention
The present invention relates to a color thermal printer having a light source.
2. Description of the Related Art
A color thermal printer for printing a full-color image is known. Such a color thermal printer uses a color thermosensitive recording paper in which at least three kinds of thermosensitive coloring layers are stacked on a base in order. For instance, the thermosensitive coloring layers include a cyan thermosensitive coloring layer, a magenta thermosensitive coloring layer, and a yellow thermosensitive coloring layer. The respective coloring layers are stacked in an order of yellow, magenta and cyan from the uppermost layer. Thermal sensitivity of the thermosensitive coloring layer becomes lower as a position thereof is lower.
The yellow thermosensitive coloring layer and the magenta thermosensitive coloring layer positioned thereunder are respectively possessed of a fixing property caused by rays of a specific wavelength band. The yellow thermosensitive coloring layer is optically fixed by applying yellow fixing rays which are violaceous rays having a wavelength of about 420 nm. Meanwhile, the magenta thermosensitive coloring layer is optically fixed by applying magenta fixing rays which are near ultraviolet rays having a wavelength of about 365 nm.
For example, as a light source for fixation, are used two fluorescent lamps of a straight-tube type constituted of a yellow fluorescent lamp and a magenta fluorescent lamp. The yellow fluorescent lamp includes a fluorescent material for emitting yellow fixing rays, and the magenta fluorescent lamp includes another fluorescent material for emitting magenta fixing rays. The yellow and magenta fluorescent lamps are arranged side by side above a conveyance passage. Further, a reflector is disposed around the respective fluorescent lamps.
When a couple of the fluorescent lamps are arranged side by side, it is difficult to downsize the printer. On account of this, in a color thermal printer described in Japanese Patent Laid-Open Publication No. 5-038823, the fixing rays are adapted to be emitted such that two kinds of fluorescent materials for emitting the respective fixing rays of yellow and magenta are separately spread on an inner wall of a glass tube of a single fluorescent lamp. This fluorescent lamp simultaneously emits the yellow and magenta fixing rays. Thus, a light shielding filter is provided to prevent the magenta fixing rays, which are emitted from the magenta fluorescent material, from being applied to a color thermosensitive recording paper during yellow fixation.
However, in order to securely shield the light, it is necessary to enlarge a size of the light shielding filter or to increase a number thereof. In doing so, there arises a problem in that it is difficult to downsize a body of the printer.